Effect of experimental DNA demethylation on phytohormones production and palatability of a clonal plant after induction via jasmonic acid

Abstract

Many plant species protect themselves against herbivores through mechanical or chemical so‐called inducible defences (ID). These are regulated via a hormonal cascade which may be under epigenetic control and in which jasmonic acid (JA) plays a prominent role. In this study, we indirectly tested the role of DNA methylation in the production of ID and the synthesis of hormones involved in the ID signalling cascade. Using different intensities of 5‐azacytidine application, we aimed to produce plants of Trifolium repens with different levels of DNA methylation alteration. We then elicited the plants together with controls, i.e. plants with natural DNA methylation status, with JA and then indirectly recorded ID production in herbivore‐choice trials in which the leaves of plants with different DNA methylation statuses were provided to caterpillars of a generalist herbivore, Spodoptera littoralis. We also analysed the balance of several key defence hormones such as jasmonates, abscisic acid (ABA), indole‐3‐acetic acid (IAA) and salicylic acid in the plants. We found that the S. littoralis preferred demethylated plants over non‐demethylated controls. Demethylation also reduced production of JA, ABA and IAA. We conclude that DNA methylation modulates expression of ID likely via regulation of signalling hormones involved in the establishment of defence.